1. Field of the Invention
The present invention relates to a method and apparatus for producing cathodes for dry-cell batteries, especially lithium batteries, whereby a pasty cathode material is pasted onto a metallic carrier material and is subsequently compressed therewith, with a current shunting being welded to an end of the carrier material.
2. Description of the Prior Art
Dry-cell batteries, i.e. nonaqueous cells, are known. In a winding-type of construction, the components, namely the electrodes and separators are superimposed upon one another as long strips and are turned to form a fixed spirally wound unit. In order to be able to produce a high-output battery, lithium in the form of a lithium foil is used as the anode. Manganese dioxide (MnO.sub.2) can be used as the cathode, so that a high-output Li/MnO.sub.2 system is obtained, with an organic electrolyte being used in which a lithium compound is dissolved as a conductive salt.
Whereas for the anode it is merely necessary to provide an appropriate metallic foil, it is more difficult to produce the cathodes for the battery, since especially MnO.sub.2 does not exist as foil, but rather as a substance that has to be applied to a metallic carrier material in order in this manner to obtain a solid cathode. In so doing, the goal is to apply the pasty cathode material onto the carrier material in a constant thickness and density, to compress the same during a fixed time period, and subsequently to provide a current shunting, whereby attention must be paid to not overstress the carrier material during manufacture. A metal mesh preferably serves as carrier material.
The production of cathodes has up to now been accomplished manually. In so doing, the carrier material, in the form of a metal mesh, is first cut to the appropriate cathode lengths and is disposed in a pasting track after first a paper strip has been provided for absorbing moisture. A weighed amount of the pasty cathode material is then manually pasted onto the carrier material, and the thus prepared cathode is subsequently compacted under a hydraulic press. Finally, after the compressing, the contact locations on one or both ends of the compacted cathode are cleaned, so that the current shuntings, which are connection strips of metal, can then be manually welded on via a spot welding procedure.
Such manually produced cathodes are not of uniform quality, so that large manufacturing tolerances and a large number of rejects are noted. Furthermore, the quantity of cathodes required can be produced only with great personnel expenditure as well as a large number of apparatus, especially for the compression.
It is therefore an object of the present invention to provide both an improved method as well as an improved apparatus for producing cathodes for dry-cell batteries, especially lithium batteries.